The present invention relates to sprayable nasal preparations which are designed to suppress rhinovirus. More particularly, it relates to buffered acidic solutions that are capable of being sprayed into a human nose and maintaining a defined pH in vivo.
Physicians have often prescribed nasal sprays to treat a variety of nasal symptoms. For example, in A. Talbot et al., 107 Laryngoscope 500-503 (1997) the authors discuss using normal or hypertonic buffered alkaline saline solutions as nasal sprays. These sprays are usually intended to treat the symptoms of a variety of nasal conditions (e.g. sinusitis).
A few mildly acidic nasal sprays are also known. Atrovent.RTM. nasal spray has a pH of about 4.7 and is believed to contain an anticholinergic agent (ipratropium bromide monohydrate), preservatives benzalkonium chloride and sodium EDTA, sodium chloride, sodium hydroxide, hydrochloric acid, and water. However, the solution is not buffered to maintain a low pH in the nose over prolonged periods.
Similarly, NasalCrom.RTM. nasal spray has a pH of 4.5-6.0 and is believed to contain cromolyn sodium in water and preservatives. Again, when challenged with even moderate dilution (with an essentially neutral pH solution), the formulation quickly reaches a neutral pH.
A product called ZICAM nasal spray (GumTech Industries) is currently claiming to reduce the effects and duration of common colds. It contains zincum gluconium in an unbufferred pH 6.7 spray solution. The effectiveness of the spray is still being evaluated. However, in any event, it requires the use of an expensive ingredient.
Other sprays and oral preparations are known that are designed to inhibit viral replication, and thereby moderate colds if given shortly before or shortly after exposure. However, such preparations again rely on the use of expensive components (e.g. ICAM-1).
The virus believed responsible for most of the symptoms attributable to a "common cold", rhinovirus, is known to be sensitive to substantially acidic pH conditions. However, this knowledge has not, to date, led to a practical therapy or technique for controlling common cold infection.
For one thing, many parts of the human body are sensitive to highly acidic conditions and will not tolerate prolonged contact with those conditions. Further, many materials (e.g. many buffers) that are acidic are not otherwise suitable for contact with a human. For example, acetates often provide an undesirable vinegar taste, ascorbates often oxidize to undesirable colors, aspartates, glutamates, and tartrates do not have desirable solubility characteristics, borates and phthalates have toxic side effects, formates don't buffer in the right pH range, and propionates and succinates produce a burning sensation.
Moreover, apart from the desirability of providing temporary symptomatic relief to a person that is infected with a virus, there is a desire (a) to inhibit the tendency of that person to spread the infection to others, (b) for persons who do not have the infection to have a preparation which will reduce the likelihood of their catching the infection from someone who has it, and (c) for there to be a way to reduce the severity and duration of the infection once it is caught. It is particularly desirable that these goals be achieved at low cost and using techniques that are well tolerated by patients.
As such, it can be seen that the need exists for an improved nasal spray and methods of using it.